The fact that surface acoustic waves will propagate on piezoelectric and other substrates has been exploited in the prior art to provide so-called surface acoustic wave (SAW) devices, which are useful in communications, radar and other signal processing systems. A SAW delay line, for example, may include an input transducer for converting input electrical signals to acoustic wave energy on the substrate and at least one output transducer for converting the acoustic wave energy back to electrical form. The acoustic wave energy propagates relatively slowly, advantageously providing delays of substantial magnitude.
Other kinds of components may be disposed on the substrate to form more complex devices. One such component is the multistrip coupler described, for example, in U.S. Pat. No. 3,836,876 issued to Marshall et al on Sept. 17, 1974, U.S. Pat. No. 3,947,783 issued to Maerfeld on Mar. 30, 1976, and U.S. Pat. No. 3,987,379 issued to DeVries on Oct. 19, 1976. A SAW multistrip coupler is comprised of an array of parallel filamentary conductors, or fingers, and is disposed on the substrate such that it lies within at least two acoustic wave paths, or "tracks". Interaction of the coupler fingers with the acoustic wave energy in one track is such as to transfer at least a portion of that energy to the other track.